Noncorrosive liquid



Patented Jan. 5, 1943 NON CORRO SIV E LIQUID Frederick B. Downing, PennsGrove, N.

or to E. I. du Pont de Nemours &

J assign- Company,

Wilmington, Del., a corporation of Delaware No Drawing. ApplicationFebruary 18, 1941, Serial No. 379,474

20 Claims.

This invention relates to non-corrosive liquids suitable for use in heatexchange devices and the like and particularly to non-corrosive aqueoussolutions of alcohols particularly adapted for use in heat exchangedevices containing iron and solder.

Heat exchange devices, and particularly the cooling systems of internalcombustion engines, are generally composed of iron and copper with partsjoined together by means of solder. Water is the cooling liquid mostcommonly employed. However, in cold weather it is usual to employaqueous solutions of non-electrolyte freezing point depressants. Thewater soluble alcohols, such as methanol, ethanol, ethylene, glycol,glycerol and the like, are generally employed as the freezing pointdepressant, particularly in internal combustion engines. It is wellknown that water alone is quite corrosive to the metals of the heatexchange devices. Aqueous solutions of the water soluble alcohols areknown to be even more corrosive than water alone. In order to overcomethis difficulty, it has become common practice to add to the coolingliquid various materials for inhibiting corrosion of the metals of theheat exchange devices by the cooling liquid.

Sodium nitrite has been recognized as a very ef-- fective corrosioninhibitor for ferrous metals, such as iron and steel, but I have foundthat it tends to increase the corrosion of solder and copper in thecooling system. Clarkson and Pedersen, in Patent 2,054,282, havedisclosed that the corrosion of copper, in heat exchange systemsemploying water or aqueous solutions of alcohols and various metalnitrites, may be inhibited by incorporating in the cooling liquid amercapto-aryl-thiazole, a hydrocarbon mercaptan or a disulfide thereof.

It is an object of the present invention to provide -an aqueous heatexchange liquid which is non-corrosive or substantially non-corrosive tothe metals of a heat exchange device, and particularly iron and solder.A further object is to provide an antifreeze liquid, employing anonelectrolyte freezing point depressant, which liquid is substantiallynon-corrosive to the heat exchanger as a whole and particularly issubstantially non-corrosive to iron and solder. A still further objectis to provide a non-electrolyte freezing point depressant which isnon-corrosive orv substantially non-corrosive to metal containers inwhich it may be transported and marketed. Other objects are toprovidenewcompositions of matter and to advance the art. Still otherobjects will appear hereinafter.

The above and other objects may be accomplished in accordance with myinvention which comprises incorporating in water, in an aqueous solutionof a non-electrolyte freezing point depressant or in a non-electrolytefreezing point depressant, and in the absence of substantial amounts ofelectrolyte, at least 0.03% of a nitrite of a metal above aluminum inthe electromotive series together with a small proportion of a watersoluble member of the group of 2-mercapto-thiazolines devoid ofnon-hydrocarbon substituents, organic acyl derivatives of such2-mercapto-thiazolines and salts of such Z-mercapto-thiazolines. I havefound that such aqueous liquids are substantially non-corrosive to themetals of the usual heat exchange devices, particularly those employedin the cooling systems of internal combustion engines, and do notmaterially affect the heat transfer coefiicient of the devices. Also,the concentrated non-electrolyte freezing point depressants, containingsuch nitrites and 2-mercapto-thiazoline compounds, are substantiallynon-corrosive to metal containers of the type ordinarily employed fortransporting and marketing them. The 2-mercapto-thiazolines, theiracylderivatives and their salts, inhibit the cor-- rosion of solder,particularly that ordinarily taking place in the presence of thenitrite, and do not prevent the nitrite from materially inhibiting thecorrosion of iron. l

By a metal above aluminum in the electromotive series, I mean the metalson the sodium side of the series. Among the nitrites, the most desirableare thoseof sodium, potassium, barium, strontium, calcium and magnesium,and particularly those of the alkali metals, such as sodium andpotassium. v

By the term non-electrolyte freezing point depressant, I means the watersoluble mono and polyhydric aliphatic alcohols which decrease thefreezing point of water when dissolved therein. By the term substantialproportions of electrolytes, I means proportions of over 5% by weight ofthe solution.

The 2-mercapto-thiazolines, their acyl derivatives and their salts,which may be employed in accordance with my invention, are thewatersoluble compounds represented by the following structural formula:

wherein each of R, R1. R2 and R3 represent hydrogen or an alkyl,aralkyl, aryl or alkaryl radical, and X represents hydrogen, an organicacyl radical or a basic salt forming element or group. 'Of thethiazoline compounds of my invention, it will 5 generally be preferredto employ the 2-mercaptothiazolines devoid of non-hydrocarbonsubstituents and particularly 2-mercapto-thiazoline itself. The nextpreferred class of compounds is the water soluble organic acylderivatives of the i0 z-mercapto-thiazolines devoid of non-hydrocarbonsubstituents, particularly the organic acyi derivatives of2-mercapto-thiazoline itself and specifically benzoyl thiazolinylsulfide.

The amount of the thiazoline compound employed may be varied from a meretrace up to about 0.5% by weight of the heat exchange liquid. Largeramounts may be employed but without advantage. About 0.01% of thethiazoline compound will be sufficient for cooling liquids employed formost automobile radiators.

In order to illustrate the advantages of my invention, the data of sometests are given in Table I.

These experimental data were obtained by immersing freshly cleanedmetaltest strips in contact with 500 cc. of a 35% solution of a commerciallydenatured ethyl alcohol, contained in a 1 liter flask, maintained at 80C. and saturated with air. The metal pieces were submitted to twoseparate 100 hour periods of exposure. At the end of each period, thetest strips were cleaned in water by rubbing with a rubber stopper,dried and weighed. Hard, adherent scale or film, formed on the metalpieces, was not removed by abrasion or chemical means, since it ispractically impossible to remove such a coating without taking some ofthe metal with it. It seems better to record positive gains in weight,rather than questionable losses obtained by a too rigorous method ofcleaning. In general, an increase or a decrease in weight of the teststrips indicates some form of corrosion. An increase, however, does notnecessarily'mean destructive corrosion since the metal may acquire aweighable film which serves to protect it from further attack. On theother hand, a significant loss in weight shows actual corrosion.

TABLE I on solder by sodium nitrite (Nos. 3 and 4). The combination ofsodium nitrite and 2-mercaptothiazoline or benzoyl thiazolinyl sulfideis, therefore, much better than sodium nitrite alone.

It will be understood that the above tests and data are given forillustrative purposes only, and that my invention is not to be limitedto the specific embodiments disclosed therein. Many variatlons andmodifications which may be made without departing from the spirit orscope of my invention will be readily apparent to those skilled in theart. Accordingly, I intend to claim my invention broadly as in theappended claims.

Amongst the variations and modifications which may be made in accordancewith my invention would comprise substituting one or more of thenitrites of the metals above aluminum in the electromotive series forthe sodium nitrite or to employ two or more nitrites of the metals abovealuminum in the electromotive series. Amounts up to about 1% by weightof the nitrites will generally be employed in practice. However, largeramounts may be employed if desired.

Also, other thiazoline compounds may be substituted for those employedin the tests. For example, one or more of R, R1, R2 and R2, in theformula previously given, may represent hydrocarbon radicalssuch asmethyl, ethyl, isopropyl, butyl, isobutyl, phenyl, tolyl, benzyl,phenylethyl and the like. Representative acyl derivatives are those inwhich X represents acetyl, propionyl, benzoyl, isopropylbenzoyl,methoxybenzoyl, chlorobenzoyl, nitrobenzoyl, phthaloyl and furoyl.Representative salts are those in which X represents sodium, potassium,trimethylammonium, diethanolammonium and tetraethylammonium.

Furthermore, my inhibitors will be found to be equally as eflective inwater alone and in aqueous solutions of other water soluble aliphaticalcohols, such as methanol, ethylene glycol and glycerol. Also, when myinhibitors are incorporated in the concentrated alcohol, they willinhibit corrosion of the metal containers in which such alcohols areordinarily packaged for storage, shipment and marketing.

The 2-mercapto-thiazoline compounds of my invention have advantages overthe Z-mercapto aryl thiazole compounds of Clarkson and Peder- Corrosionof steel and solder in 35% aqueous ethyl alcohol It will be observedthat the corrosion of steel, in uninhibited aqueous alcohol, is highwhile that of solder is slight (No. 1). The addition of 0.088% of sodiumnitrite greatly reduces the corrosion of steel but increases that ofsolder (No. 2). The further addition of 0.009% of either2-mercapto-thiazoline or benzoyl thiazolinyl sulfide, althoughdecreasing slightly the protection of lteel by to which they sodiumnitrite, greatly reduces the attack sen, in Patent 2 and more stabl tooxidation on 954,282, of being more soluble e, that is, they are moreresistant storage and under the conditions are subject in automobileradiy corrosion inhibitors may be emositions such as those disclosed byPedersen, in Patent 2,087,098, and Pedersen, in Patent 2,087,103. Insion inhibitors are particularly deators. Also, m ployed in compSpiegler and Downing and fact, my corro signed to be substituted for thecorrosion inhibitors employed in compositions of the type disclosedinPatent 2,087,103.

I. claim:

1. A non-corrosive liquid, suitable for use in heat exchange devices andthe like containing iron and solder, which comprises water havingincorporated therein at least 0.03% of a nitrite of a metal abovealuminum in the electromotive series and a small proportion of awater-soluble member of the group consisting of 2-mercaptothiazolinesdevoid of non-hydrocarbon substituents, organic acyl derivatives of suchZ-mercaptothiazolines and salts of such Z-mercapto-thiazolines, in theabsence of substantial proportions of electrolytes.

2. A non-corrosive liquid, suitable for use in heat exchange devices andthe like containing iron and solder, which comprises water havingincorporated therein at least 0.03% of a nitrite of a metal abovealuminum in the electromotive series and a small proportion of awater-soluble Z-mercapto-thiazoline devoid of non-hydrocarbonsubstituents, in the absence of substantial proportions of electrolytes.

3. A non-corrosive liquid, suitable for use in heat exchange devices andthe like containing iron and solder, which comprises water havingincorporated therein at least 0.03% of a nitrite of a metal abovealuminum in the electromotive series and a small proportion of2-mercapto-thiazoline, in the absence of substantial proportions ofelectrolytes.

4. A non-corrosive liquid, suitable for use in heat exchange devices andthe like containing iron and solder, which comprises water havingincorporated the rein at least 0.03 of a nitrite of a metal abovealuminum in the electromotive series and a small proportion of awater-soluble organic acyl derivative of a 2-mercapto-thiazoline devoidof non-hydrocarbon substituents, in the absence of substantialproportions of electrolytes.

5. A non-corrosiveliquid, suitable for use in heat exchange devices andthe like containing iron and solder, which comprises water havingincorporated therein at least 0.03% of a nitrite of a metal abovealuminum in the electromotive series and a small proportion of awater-soluble aromatic acyl derivative of 2-mercapto-thiazoline, in theabsence of substantial proportions of electrolytes.

6. A non-corrosive liquid, suitable for use in heat exchange devices andthe-like containing iron and solder, which comprises water havingincorporated therein at least 0.03% of a nitrite of a metal abovealuminum in the electromotive series and a small proportion of benzoylthiazolinyl sulfide, in the absence of substantial proportions ofelectrolytes.

7. A non-corrosive liquid, suitable for use in heat exchange devices andthe like containing iron'and solder, which comprises water and awater-soluble aliphatic alcohol having incorporated therein at least0.03% of an alkali metal nitrite and a, small proportion of awater-soluble member of the group consisting of Z-mercaptothiazolinesdevoid of non-hydrocarbon substituents, organic acyl derivatives of such2-mercaptothiazoiines and salts of such 2-mercapto-'thiazolines, in theabsence of substantial proportions of electrolytes.

8. A non-corrosive liquid, suitable for use in heat exchange devices andthe like containing iron and solder, which comprises water and a 3water-soluble aliphatic alcohol having incorporated therein at least0.03% of an alkali metal nitrite and a small proportion of awater-soluble 2-mercapto-thiazoline devoid of non-hydrocarbonsubstituents, in the absence of substantial proportions of electrolytes.

9. A non-corrosive liquid, suitable for use in heat exchange devices andthe like containing iron and solder, which comprises water and awater-soluble aliphatic alcohol having incorporated therein at least0.03% of an alkali metal nitrite and a small proportion ofZ-mercaptothiazoline, in the absence of substantial proportions ofelectrolytes.

10. A non-corrosive liquid, suitable for use in exchange devices and thelike containing iron and solder, which comprises water and awater-soluble aliphatic alcohol having incorporated therein at least0.03% of an alkali metal nitrite and a small proportion of awater-soluble organic acyl derivative of a Z-mercapto-thiazoline devoidof non-hydrocarbon substituents, in the absence of substantialproportions of electrolytes.

11. A non-corrosive liquid, suitable for use in heat exchange devicesand the like containing iron and solder, which comprises water and awater-soluble aliphatic alcohol having incorporated therein at least0.03% of an alkali metal nitrite and a small proportion of awater-soluble aromatic acyl derivative of a Z-mercapto-thiazoline devoidof non-hydrocarbon substituents, in the absence of substantialproportions of electrolytes.

12. A non-corrosive liquid, suitable for use in heat exchange devicesand the like containing water-soluble aliphatic alcohol havingincorporated therein at least 0.03% of an alkali metal nitrite and asmall proportion of benzoyl thiazolinyl sulfide, in the absence ofsubstantial proportions of electrolytes.

13. A water-soluble aliphatic alcohol having incorporated therein asmall proportion of a nitrite of a metal above aluminum in theelectromotive series sufiicient to inhibit corrosion of ferrous metalsby the alcohol and a small proportion of a water-soluble member of thegroup consisting of Z-mercapto-thiazoline devoid of nonhydrocarbonsubstituents, organic acyl derivatives of such Z-mercapto-thiazolinesand salts of such Z-mercapto-thiazolines, in the absence of substantialproportions of. electrolytes.

14. A water-soluble aliphatic alcohol having incorporated therein asmall proportion of a nitrite of a metal above aluminum in theelectromotive series suflicient to inhibit corrosion of ferrous metalsby the alcohol and a small proportion of a water-soluble2-mercapto-thiazoline devoid of non-hydrocarbon substituents, in theabsence of substantial proportions of electrolytes.

15. A water-soluble aliphatic alcohol having incorporated therein asmall proportion of a nirous metals by the alcohol and a smallproportion 01' a water-soluble organic acyl derivative of a 2-mercapto-thiazoline devoid of non-hydrocarbon substituents, in theabsence of substantial proportions of electrolytes.

17. A water-soluble aliphatic alcohol having incorporated therein asmall proportion of a nitrite of a metal above aluminum in theelectromotive series sufficient to inhibit corrosion of ferrous metalsby the alcohol and a small proportion of benzoyl thiazolinyl sulfide, inthe absence of substantial proportions of electrolytes.

18. A non-corrosive liquid, suitable for use in heat exchange devicesand the like containing iron and solder, which comprises water havingincorporated therein at least 0.03% of sodium nitrite and a smallproportionof z-mercapto-thiazoline, in the absence of substantialproportions 15 of electrolytes.

asomw FREDERICK B. DOWNING.

